Numerical Investigation of a Process Control for the Roller Levelling Process Based on a Force Measurement

Abstract

When processing conventional semi-finished metal strips, distinctive changes in the material properties along the strip length are unavoidable. The roller levelling process is sensitive to changes of those strip characteristics. Thus, a process control allowing for an online adaption of the roller levelling machine according to the actual strip characteristics is highly desirable. In order to enable a precise process layout, the calculation by the Finite Element Method (FEM) provides a suited strategy. Furthermore, the coupling of user-subroutines to an FE code offers the possibility to implement and test respective control strategies. This work proposes a control strategy that is based on a force measurement in the first load triangle of a levelling machine. A first FE model including a feedback control is used to calculate the dependence between the force in the first load triangle and the roll intermesh in the last load triangle leading to a flat sheet. The results are transferred to meta models – so called control curves – that give a direct relationship between the measured force and the roll intermesh. Within a second FE setup a feed-forward control based on these control curves is implemented and the proposed control strategy is investigated for varying yield strengths along the strip length. Thus, the time consuming FE simulations that are necessary to obtain the control curves are decoupled from the actual levelling process. According to the obtained results, the introduced approach is able to improve the sheet flatness for thin sheets when a change in the material properties occurs.

Novel Straightening-Machine Design with Integrated Force Measurement for Straightening of High-Strength Flat Wire

“…These, in turn, led to uneven loads on the force-measurement rings due to the resulting deformations and necessitated further modifications of the measurement concept to mitigate this effect. A very similar machine was used in [2,3,13]. However, the force measurement concept made use of conventional load cells placed in between the roller and the driving end of the spindles.…”

“…Vertical movement of the three upper rollers was enabled by mounting them to the lower part of the straightening units, each consisting of two linear bearing blocks with a load cell screwed in between. To provide translational movement, the upper bearing blocks were outfitted with spindle threads which enabled moving the straightening units via three spindles connected to A very similar machine was used in [2,3,13]. However, the force measurement concept made use of conventional load cells placed in between the roller and the driving end of the spindles.…”

Innovative Measurement Of Stress Superposed Steel Strip For Straightening Machines

“…These numerical investigations are used to identify a suitable set up of the straightening roll infeed and the state of stress within the material [5][6][7][8]. But not only numerical calculations are expedient, analytical models can help as well to provide information concerning the infeed of the straightening rolls, as shown in [9][10][11][12].…”

A Novel Modeling Method in Metal Strip Leveling Based on a Roll-Strip Unit

“…Stadler et al investigated the curvature and the contact force at the striproll contact point of a metal strip in an experimental device and derived a material model and a steady-state strip deformation model to compute the feasible combinations of curvature and contact force [29]. Grüber and Hirt proposed a control strategy on a force measurement in the first load triangle of a leveling machine and investigated a feedforward control strategy based on control curves for varying yield strengths along the strip length [30,31]. Nikula et al analyzed the mechanical stress inflicted on a roller leveler processing cold steel strips based on a feature extracted from vibration measurements and introduced models specific to different steel grades to the prediction of the stress level [32,33].…”